基于对等SIP协议的IP电话在手机上的研究与实现
摘要
VoIP是下一代网络中一个极其重要的应用,作为构建VoIP电话系统信令协议之一的SIP协议,以其突出的简单、灵活、分布式控制和易于扩展等优点赢得了业界的青睐,尤其是在3G即决定使用SIP协议作为其多媒体域的控制协议之后,基于SIP协议的研究成为IP电话研究领域的热点。
随着无线宽带化的进程不断加快,原来在无线数据通信网中被视为应用“瓶颈”的带宽和服务质量等问题一一得到解决,如何在智能手机等嵌入式移动终端上设计和实现高性能的IP电话,是IP电话发展的一个重要方向。目前,基于SIP协议的IP网络电话系统大部分是C/S结构的,这种系统存在服务器的瓶颈问题,而且不容易在一个小环境(如:紧急通信或会议)中迅速部署系统。
针对这一状况,本文主要做了以下工作:
1)详细剖析了VoIP的关键技术之一:SIP。对现有的SIP体系结构做了改进与扩展使其能适应对等的网络拓扑结构;
2)对在基于Windows Mobile的嵌入式移动终端上设计一套SIP IP Phone涉及到的技术问题做了详细分析,设计了一套具有高可移植性的软件体系结构;
3)通过改进开源的osip栈,完成了SIP协议的事务管理模型。为适应对等的SIP结构,对开源osip栈的状态机部分做了较大的改进与重设计,增加了协调信令与媒体协议的电话应用状态机,并对osip栈并未涉及的底层传输模型做了设计与实现。
4)设计实现了一套实时语音采集播放框架,并分析了为提高语音质量采用的策略。
5)设计实现了一套定时器管理机制,以便对应用层协议中定义的大量定时器做高精度的支持。
基于SIP协议的IP电话在嵌入式移动平台的应用中有着很大的潜力,有待于进一步的研究与探索。在本文的结尾部分,对SIP协议的研究扩展的下一步工作做出了展望。
VoIP is one of the most important applications in the Next Generation Network. SIP(Session Initiation Protocol) is one of the signaling protocols to develop the VoIP system. SIP is simple, flexible,distributed controled and easy to be extended. As 3GPP has adopted SIP as the controlling protocol for the IP Multimedia Subsystem, the research of SIP is becoming a spotlight in the field of IP telephony.
With the development of high bandwidth wireless communications, the bandwidth and QoS issue are no longer the obstacle for deploying networking and multimedia applications on mobile devices over wireless network.To develop and deploy a high performance IP telephony over mobile devices is feasible and can provide seamless connectivity to the VoIP end user.However, the current SIP based VoIP applications use C/S archetecture, which is hard to be deployed in a small group meeting situation with ease.
The contribution and feature of this paper includes:
1) Analysed the SIP protocol, which is one of the key technologies in VoIP. Worked out extensions for the current SIP archetecture to adapt to the peer to peer network archetecture.
2) Discussed key technical issues in designing a SIP based IP telephony under windows mobile devices, designed a software archetecture with high portability.
3) Designed a SIP transaction model based on gnu osip protocol stack. Enhanced the existing osip stack with an applicatin-state-machine to harmonize the signalling and media transactions. Designed the SIP transport layer which is not mentioned in the osip stack.
4) Designed a realtime audio gathering and playback subsystem, with enhanced realtime audio playback quality.
5) Designed a high performance session timer mechanism to support multiple session timers in the SIP statemachine.
The SIP based telephony is a promising technology in the embedded and mobile environment, thus is worthwhile for future research and discussion. In the end of this paper, the prospect of SIP extension was described to provide a guideline for the futurework.
随着无线宽带化的进程不断加快,原来在无线数据通信网中被视为应用“瓶颈”的带宽和服务质量等问题一一得到解决,如何在智能手机等嵌入式移动终端上设计和实现高性能的IP电话,是IP电话发展的一个重要方向。目前,基于SIP协议的IP网络电话系统大部分是C/S结构的,这种系统存在服务器的瓶颈问题,而且不容易在一个小环境(如:紧急通信或会议)中迅速部署系统。
针对这一状况,本文主要做了以下工作:
1)详细剖析了VoIP的关键技术之一:SIP。对现有的SIP体系结构做了改进与扩展使其能适应对等的网络拓扑结构;
2)对在基于Windows Mobile的嵌入式移动终端上设计一套SIP IP Phone涉及到的技术问题做了详细分析,设计了一套具有高可移植性的软件体系结构;
3)通过改进开源的osip栈,完成了SIP协议的事务管理模型。为适应对等的SIP结构,对开源osip栈的状态机部分做了较大的改进与重设计,增加了协调信令与媒体协议的电话应用状态机,并对osip栈并未涉及的底层传输模型做了设计与实现。
4)设计实现了一套实时语音采集播放框架,并分析了为提高语音质量采用的策略。
5)设计实现了一套定时器管理机制,以便对应用层协议中定义的大量定时器做高精度的支持。
基于SIP协议的IP电话在嵌入式移动平台的应用中有着很大的潜力,有待于进一步的研究与探索。在本文的结尾部分,对SIP协议的研究扩展的下一步工作做出了展望。
VoIP is one of the most important applications in the Next Generation Network. SIP(Session Initiation Protocol) is one of the signaling protocols to develop the VoIP system. SIP is simple, flexible,distributed controled and easy to be extended. As 3GPP has adopted SIP as the controlling protocol for the IP Multimedia Subsystem, the research of SIP is becoming a spotlight in the field of IP telephony.
With the development of high bandwidth wireless communications, the bandwidth and QoS issue are no longer the obstacle for deploying networking and multimedia applications on mobile devices over wireless network.To develop and deploy a high performance IP telephony over mobile devices is feasible and can provide seamless connectivity to the VoIP end user.However, the current SIP based VoIP applications use C/S archetecture, which is hard to be deployed in a small group meeting situation with ease.
The contribution and feature of this paper includes:
1) Analysed the SIP protocol, which is one of the key technologies in VoIP. Worked out extensions for the current SIP archetecture to adapt to the peer to peer network archetecture.
2) Discussed key technical issues in designing a SIP based IP telephony under windows mobile devices, designed a software archetecture with high portability.
3) Designed a SIP transaction model based on gnu osip protocol stack. Enhanced the existing osip stack with an applicatin-state-machine to harmonize the signalling and media transactions. Designed the SIP transport layer which is not mentioned in the osip stack.
4) Designed a realtime audio gathering and playback subsystem, with enhanced realtime audio playback quality.
5) Designed a high performance session timer mechanism to support multiple session timers in the SIP statemachine.
The SIP based telephony is a promising technology in the embedded and mobile environment, thus is worthwhile for future research and discussion. In the end of this paper, the prospect of SIP extension was described to provide a guideline for the futurework.
引文
[1]周海华,边恩炯.《下一代网络SIP原理与应用》.机械工业出版社,2006:1-134.
[2]黄永峰.IP网络多媒体通信技术.人民邮电出版社,2003:23-35
[3]ITU-T Rec.H.323.Packet based Multimedia Communications Systems,v.2,1998.
[4]Session Initial Protocol,RFC3261.
[5]陆立.NGN协议原理及应用.机械工业出版社,2004:67-89.
[6]Clint Smith.Daniel Collins著.李波等译.第3代无线通信网络.人民邮电出版社,2003:3-6
[7]计育青.VoIP迈向主流应用.中国电子报,2002.06:4-6
[8]黄永峰等编著.IP网络多媒体通信技术.人民邮电出版社,2003:23-35
[9]王琦,马跃,喻炜.VoIP中为保证语音质量所采用的关键技术.北京邮电大学计算机与科学技术学院
[10]H.Schulzrinne,S.Casner,R.Frederick et al.RFC 3550.RTP:A Transport Protocol for Real-Time Applications.July 2003:157-198
[11]Daniel Collins编著.李勇译.VoIP技术与应用.人民邮电出版社
[12]Private Extensions to the Session Initiation Protocol(SIP) for Asserted Identity within Trusted Networks,RFC3325
[13]The SIP INFO Method.RFC2926
[14]A Presence Event Package for the Session Initiation Protocol(SIP).RFC3856
[15]The Session Initiation Protocol(SIP) Refer Method.RFC3525
[16]赵慧玲,叶华.以软交换为核心的下一代网络技术.人民邮电出版社
[17]隋晋光,鲁士文.P2PSIP技术的研究.电子技术与应用,2007年6月,Vol6
[18]朱小军.SIP协议在WiFi手机中的应用与实现.电子科技大学研究生学位论文,2006
[19]Gonzalo Camarillo,白建军,彭晖,田敏 译.SIP揭秘.人民邮电出版社2003年6月
[20]司端锋,韩心慧,龙勤,潘爱民.SIP标准中的核心技术与研究进展.软件学报,2005年1月vol16,No.2
[21]SDP:Session Description Protocol.RFC2327
[22]徐传福.基于P2P的广域网内容发布系统关键技术研究.国防科学技术大学研究生院学位论文,2003
[23]江雪阳.基于P2P的分布存储系统的定位与复制算法研究.国防科学技术大学研究生院学位论文,2003
[24]赖聪.基于P2P的SIP网络电话关键技术的研究.北京邮电大学研究生学位论文,2006
[25]乐光学,李仁发,周祖德.基于Region多层结构P2P计算网络模型.软件学报,2005年1月,Vol16,No6
[26]Balakrishnan H,Kaashoek MF,KargerD,et.Looking up data in p2p systems.Communications of the ACM,2003.
[27]S.Ratnasamy,M.Handley,R.Karp,and S.Shenker.Topologically aware overlay construction and server selection,in Proc.INFOCOM'02,New York,USA,Jun.2002.
[28]Y.-H.Chu,A.Ganjam,T.S.E.Ng,S.G.Rao,K.Sripanidkulchai,J.Zhan and H.Zhang.Early deployment experience with an overlay based Internet broadcasting system.USENDIX Annual Technical Conference,Jun.2004.
[29]Robert Morris,David Kagre,M.Frans Kaashoek.Chord:A Scalable Peer to Peer Lookup Sevrice of Internet Applications.MIT Laboratory for Computer Science,2003
[30]Antony Rowstron and Peter Druschel.Pastry:Scalable,decentralized object location and routing for large-scale peer-to-peer systems.ACM International Conference on Distributed Systems Platforms(Middleware 2001),2001
[31]陈端.P2P SIP技术进展.电信网技术,2007年7月,Vol7
[32]Singh.K.and H.Schulzrmne.Peer-to-peer Internet Telephony using SIP.Proceedings of the 2005 Network and Operating Systems Support for Digital Audio and Video Workshop(NOSSDAV),June 2005
[33]Yang B,Garcia-Molina H.Improving search in peer-to-peer networks.In:Sivilotti PACked.Proc.of the Int'l Conf.on Distributed Computing Systems[C].IEEE Computer Society,2002
[34]http://msdn2.microsoft.com/en-us/embedded/aa714541.aspx
[35]李庆诚,唐德凯.嵌入式操作系统实时性比对与评价.单片机与嵌入式系统应用,2007.6
[2]黄永峰.IP网络多媒体通信技术.人民邮电出版社,2003:23-35
[3]ITU-T Rec.H.323.Packet based Multimedia Communications Systems,v.2,1998.
[4]Session Initial Protocol,RFC3261.
[5]陆立.NGN协议原理及应用.机械工业出版社,2004:67-89.
[6]Clint Smith.Daniel Collins著.李波等译.第3代无线通信网络.人民邮电出版社,2003:3-6
[7]计育青.VoIP迈向主流应用.中国电子报,2002.06:4-6
[8]黄永峰等编著.IP网络多媒体通信技术.人民邮电出版社,2003:23-35
[9]王琦,马跃,喻炜.VoIP中为保证语音质量所采用的关键技术.北京邮电大学计算机与科学技术学院
[10]H.Schulzrinne,S.Casner,R.Frederick et al.RFC 3550.RTP:A Transport Protocol for Real-Time Applications.July 2003:157-198
[11]Daniel Collins编著.李勇译.VoIP技术与应用.人民邮电出版社
[12]Private Extensions to the Session Initiation Protocol(SIP) for Asserted Identity within Trusted Networks,RFC3325
[13]The SIP INFO Method.RFC2926
[14]A Presence Event Package for the Session Initiation Protocol(SIP).RFC3856
[15]The Session Initiation Protocol(SIP) Refer Method.RFC3525
[16]赵慧玲,叶华.以软交换为核心的下一代网络技术.人民邮电出版社
[17]隋晋光,鲁士文.P2PSIP技术的研究.电子技术与应用,2007年6月,Vol6
[18]朱小军.SIP协议在WiFi手机中的应用与实现.电子科技大学研究生学位论文,2006
[19]Gonzalo Camarillo,白建军,彭晖,田敏 译.SIP揭秘.人民邮电出版社2003年6月
[20]司端锋,韩心慧,龙勤,潘爱民.SIP标准中的核心技术与研究进展.软件学报,2005年1月vol16,No.2
[21]SDP:Session Description Protocol.RFC2327
[22]徐传福.基于P2P的广域网内容发布系统关键技术研究.国防科学技术大学研究生院学位论文,2003
[23]江雪阳.基于P2P的分布存储系统的定位与复制算法研究.国防科学技术大学研究生院学位论文,2003
[24]赖聪.基于P2P的SIP网络电话关键技术的研究.北京邮电大学研究生学位论文,2006
[25]乐光学,李仁发,周祖德.基于Region多层结构P2P计算网络模型.软件学报,2005年1月,Vol16,No6
[26]Balakrishnan H,Kaashoek MF,KargerD,et.Looking up data in p2p systems.Communications of the ACM,2003.
[27]S.Ratnasamy,M.Handley,R.Karp,and S.Shenker.Topologically aware overlay construction and server selection,in Proc.INFOCOM'02,New York,USA,Jun.2002.
[28]Y.-H.Chu,A.Ganjam,T.S.E.Ng,S.G.Rao,K.Sripanidkulchai,J.Zhan and H.Zhang.Early deployment experience with an overlay based Internet broadcasting system.USENDIX Annual Technical Conference,Jun.2004.
[29]Robert Morris,David Kagre,M.Frans Kaashoek.Chord:A Scalable Peer to Peer Lookup Sevrice of Internet Applications.MIT Laboratory for Computer Science,2003
[30]Antony Rowstron and Peter Druschel.Pastry:Scalable,decentralized object location and routing for large-scale peer-to-peer systems.ACM International Conference on Distributed Systems Platforms(Middleware 2001),2001
[31]陈端.P2P SIP技术进展.电信网技术,2007年7月,Vol7
[32]Singh.K.and H.Schulzrmne.Peer-to-peer Internet Telephony using SIP.Proceedings of the 2005 Network and Operating Systems Support for Digital Audio and Video Workshop(NOSSDAV),June 2005
[33]Yang B,Garcia-Molina H.Improving search in peer-to-peer networks.In:Sivilotti PACked.Proc.of the Int'l Conf.on Distributed Computing Systems[C].IEEE Computer Society,2002
[34]http://msdn2.microsoft.com/en-us/embedded/aa714541.aspx
[35]李庆诚,唐德凯.嵌入式操作系统实时性比对与评价.单片机与嵌入式系统应用,2007.6